Technical Report of ISSP Ser. A: Number 3024

Abstract

In the orbitally degenerate (J = 5/2) Periodic Anderson Model, the magnetic susceptibility is composed of both the Pauli term and the Van Vleck term, as is well known. The former is strongly enhanced by the strong correlation between f-electrons. But, for the latter, the influence of the strong correlation has been obscure for years. In this paper the solution of the longstanding problem is presented. With the aid of the d = infinity approximation, this problem on the basis of the Fermi liquid theory is studied with degenerate orbitals taking account of all the vertex corrections in a consistent way. As a result, it is shown unambiguously that the Van Vleck term is also highly enhanced in the strong correlation regime. This fact explain naturally the enhanced magnetic susceptibility observed in many insulating systems (i.e., Kondo insulator). Moreover, it is shown that the Wilson ratio takes a value around 1 in the metallic system, in good agreement with experiments.

縮退軌道(J=5/2)周期的Andersonモデルでは、帯磁率はよく知られたようにPauli項とVan Vleck項の両者から成る。前者はf電子間の強相関によって強く増進する。しかし、後者に対しては強相関の影響は永年はっきりしなかった。この論文では積年の問題の解を与えた。d=∞近似の助けを得て、無撞着法であらゆる頂点補正を考慮する軌道縮退のあるFermi液体理論の基礎に基づいてこの問題を検討した。結果として、強相関系でもVan Vleck項もまた高度に増進させられることを明白に示した。この事実は多くの絶縁系(例えば近藤絶縁体)で観測された増進した帯磁率を自然に説明する。その上にWilson比は金属系の実験とよく一致してほぼ1の値をとることも示した。